NIMROD TEAM MEETING Monday, Feb 2 SAIC SAN DIEGO Monday 2 Feb. 1. STATUS OF CODE - Advection Predictor-corrector. Same status as at APS. Carl is looking into upwinding with finite elements. Truncation errors in Ohm's law may lead to spurious numerical resistivity and reconnection. - Two Fluid Nothing new since APS. This is not a priority until we pass the GA acceptance test. - Pressure Nothing new since APS. - Vacuum/Separatrix Carl and Tom have completed triangulation of the vacuum region. It is ready for Dalton and Alexander to start the vacuum/plasma problem. This can only run with EFIT equilibria, not TOQ. - Organization Code has been reorganized and cleaned up since APS. Take new draw.in files from the package. Management/integrand routine interface has been cleaned up. 2, CODE PERFORMANCE Linear Solver: iterative solve takes 75 to 80 percent of the time in NIMROD. Alfonso has compared ISIS with the NIMROD solver on a NIMROD matrix. The problem was a square grid with wave propagation. ISIS seems to be about a factor of 2 faster on a big 32 processor problem (factor of 3 for single processor). Care should be taken that the tolerances and norms are the same for the 2 cases. Steve has been looking at the same type of comparison with AZTEC. The problem was a circular grid with a central tblock. Got a factor of 2 faster single processor performance. We need to test the hardest or most relevant case with both of these packages. NIMROD F90 package has: - Block Jacobi - Block direct (different block) - Block ILU_0,1 -1D direct solve along a grid line. (new since APS, in the readme and input.f files) (these are really "line Jacobi") DECISION: Alfonso and Steve will continue to test ISIS and AZTEC. Tests will be done on the same problem. This problem will be typical of a hard NIMROD physics problem, including the degenerate rblock and tblocks. Alfonso will use the same driver as Steve. They should verify the speedup we can expect from using one of these packages. Then we can make the decision on whether to incorporate thee packages into NIMROD. Single Processor Performance: nothing new. Alan thinks everything is "fine". We'll revisit this when the solver gets optimized. Parallel FFTs: Steve and Carl have looked at parallelizing over both grid blocks and Fourier modes. This way we could get parallelization over the third dimension. Concensus: Steve and Carl should continue to pursue this, but Steve should make the linear solver his top priority. The Dreaded Jaggies: These occur in a linear tearing mode problem, not near the singular surface but near the boundary. Alan has identified the cause as imperfect cancellation between two terms in the linearized Lorentz force. The cure is to re-organize the force into conservation form. This allows the finite element formulation of the terms in the Lorentz force to balance. This also introduces a numerical parallel force proportional to divB. This can be cured by a well known method due to Barnes and Brackbill. This has not yet been verified in practice. Use of T3E Allocation: Everyone will be reasonable. We'll try to get more time through Mike Crisp. Dalton will try to remember to send out status setcub reports every 2 weeks. Everyone will learn to use setcub itself. 3. VALIDATION PLAN Required Linear Benchmarks: GATO ideal kink: Done except for poloidal variation in vphi. This seems to be a temporal convergence issue. This is complete. Soloviev: Convergence studies are complete. Good agreement with Berger, et al. Toroidal Resistive Modes: Comparison with FAR for S=10**7. Scott is running these. He had some normalization problems with the case. Rumors are that he has gotten some good results in the last few days. Tom will check his e-mail for results. Galkin case: Carl and Alfonso have tried to run this. They get too fast growth rate, but may be converging on eigenfunction. This is still being investigated. Whistler waves and 2-fluid effects: Effect on growing modes in DEBS is unacceptably large. This is the same algorithm as in NIMROD, except that NIMROD doesn't have the electron pressure yet. We probably need an antisymmetric solver to get this right. Nonlinear cases: DIIID: n=0 and 1 done, with no advection. Needs to be re-run with more modes and advection. Cylindrical tearing: Nonlinear saturation comparison with DEBS has been done. Finite (R/a) RFP: Theta=1.6 case reverses and sustains with nonlinear dynamo (n=0,10), R/a=2. Probably need more modes (n=20??). Ballooning (Linear): Eigenfunction looks good (n=10). Growth rate vs. beta has been calculated. Results are consistent from DCON, and with growth rate estimates. GA Acceptance Criteria: We'll see. Collaboration with Keldysh: Sergei Galkin gave a presentation on the work done at Keldysh in support of NIMROD. He gave us a proposal for the next years work, and we will take it under advisement for discussion with DOE, who eventually funds the work. (Thus was given on Tuesday morning, 2/3.) 4, STATUS OF GUI Tom has kept it up to date. The customers (GA) will give us the best feedback. Remote operation on the T3E has not yet been defined by the customer. We'll need to get feedback on this from the GA beta test. Tuesday, Feb. 3 5. GRAPHICS AND VISUALIZATION Alan talked about ANALYZE and NIMPLOT. ANALYZE is an automated, non-interactive version of NIMPLOT. ANALYZE will be able to generate all types of output in all types of formats. Analyze needs to be generated to handle multiple Fourier modes. Poincare plots will be added to both ANALYZE and NIMPLOT. Alan is responsible for ANALYZE. Carl is responsible for NIMPLOT. XDRAW is now fully functional on the T3E. 6. DEVELOPMENT Gridding of Vacuum Region: The code is ready for implementation of the nonlinear vacuum-plasma interface problem. Tblocks and gridding of the vacuum region have been implemented. Alan will begin work on extending the concept of flux coordinates into the vacuum region so that we can use rblocks to the maximum extent possible. Carl and Dalton will implement the vacuum region algorithm. Grid Packing near Rational Surfaces: Alan is starting to think about this problem. He won't start on this until he cures the dreaded jaggies. Resistive Wall Formulation: Alexander gave a presentation and a write up about a possible resistive wall formulation. It amounts to a time dependent boundary condition. It would be easier to implement in the wall resistivity is small so that it could be done explicitly. Everyone seems to be happy with this formulation. Alan thinks we may be able to adapt Morrl Chance's code for this task, but not everyone agrees. Alexander will perform this task. He will set up a collaboration with Morrel. Neoclassical Stuff: Tom is working on a self-consistent formulation of the viscous stress tensor. 7. DOCUMENTATION Dalton has completed 15 pages of summary documentation. He and Alfonso will find the best way to get it onto the web site. We are reminded that SAIC is responsible for the web site, so Alfonso will fix the existing problems with the html pointers. Alan is moving the nimrod e-mail reflector to nimrod.lanl.gov. 8. MANAGEMENT CVS: Carl is librarian. He is the only one who can update the master copy. On nimrod you need: ==> setenv CVSROOT /usr/local/cvs cvs so nimrod ==> check out nimrod cvs diff ==> gives listing of changes cvs update [filename] ==> flags conflicts, update if none cvs export -r [HEAD] [nimrod2_1] nimrod==> get source files 9. MEETINGS/PAPERS Sherwood: Abstracts due Feb. 11 1. Tearing modes: Alan, Scott?? 2. Ballooning modes/Nonlinear internal kink: Tom 3. Status/Review: Carl 4. Soloviev: Alfonso,Dalton Dalton will not attend Sherwood. Alan will run and organize the team meeting at Sherwood. EPS: Alan is giving an invited talk at EPS. in June/July IAEA: Yokohama in 10/98. Abstracts due end of March. We intend to submit an abstract and we'll wait and see what we have by the middle of March. 10. OTHER BUSINESS Budgets, etc. Advisory board: ??? decision postponed. 12. TIME AND DATE FOR NEXT: Meeting: Sherwood Teleconference: Thursday February 19, 12-2pm EST, 9am-11am PST.